1. Field of the Invention
This invention relates to the field of pipeline fluid or pipeline gas handling systems, and particularly pipeline sample cylinder end caps.
2. Related Art
The following term(s) as used herein have the following meanings: "straight" means without sharp bends or sudden changes in direction, so even a slight angle or curve is straight for the purpose of this application, the essence of "straight" merely being to minimize blockage in ducts.
Sample cylinders are utilized in pipeline system applications. Sample cylinders automatically sample a product being routed through a pipeline. End caps on the sample cylinders have internal purging and inlet ducts whereby the product enters for sampling and exits after sampling during purging. Several samples may be taken over a given period of time. After each sample is taken the sample cylinder is purged. It is essential that a given sample is purged completely so that residue from a given sample does not cross contaminate subsequent samples. If dead space exists in the end cap or in the sampling chamber of the sample cylinder or at the interface between the end cap and cylinder where residual material can get trapped and the dead space is in an area that is difficult to purge, then this is a problem that requires resolving. Also, residual material can get trapped in the inlet or purging ports because of contours or bends in the port that disrupt a direct and straight flow path of fluid. Such areas where residual material can be trapped are sometimes difficult to purge.
Current end cap designs for sample cylinders have a generally cylindrical flanged plug structure. The flanged plug design acts as a closure member for the sample cylinder. The plug portion of the closure member axially inserts into the end opening of the sample cylinder thereby plugging the sample cylinder. Also, current end cap and sample cylinder designs tend to have an o-ring seal that is installed circumferencially around the end cap plug end and around the generally cylindrical piston that is axially displaced within the sample cylinder. O-ring seals are usually installed in a radially recessed groove. With this design dead-space may exist around the o-ring seal.
This problem with end cap and sample cylinder designs have not been effectively addressed by any known prior art patents.
The are some prior art patents that address the use of sample cylinders and the various end cap designs and there are some patents that address seal designs. None are designed to eliminate the problem of dead space around o-ring seals used on end caps and pistons of sample cylinders which causes residual material to be trapped.
U.S. Pat. No. 3,712,631 issued Jan. 23, 1973 to Forchina shows a sealing gasket for the joint between spigot pipes. The invention relates to a sealing means for pipe joints where a joint is formed by coaxially inserting one pipe into an adjoining pipe. This joint is similar to the joint formed when an end cap is coaxially press fit into the end of a sample cylinder, or to the seal formed when the piston is axially displaced within the sample cylinder. However when the patent is examined it is obvious that the dead space will still exist around the seal if this seal is utilized. The preferred embodiment shows a seal having a triangular cross section. This geometry will not eliminate the problem.
U.S. Pat. No. 4,628,750 issued Dec. 16, 1986, to Welker shows an integrated pump and sample vessel. This invention uses the same flanged plug end cap design and sample cylinder piston described above, thereby having the problems described above. Residual material may get trapped around the o-ring seal.
U.S. Pat. No. 3,071,386 issued Jan. 1, 1963, to Scannell shows annular multi-element wedge shaped seals. The invention is particularly concerned with providing a seal for sealing a clearance between two relatively movable cylindrical parts arranged in an assembly wherein one part moves axially with respect to the other part. However, the purpose of this invention is to seal the clearance between to cylindrical surfaces, whereas the subject problem is not related to sealing clearances between two laterally disposed cylindrical surfaces. It is related to closing up recessed gaps or hidden crevices denoted as "dead space" between the component being sealed and the seal itself.
A practical solution for a sample cylinder end cap design that will eliminate the problem with residual material being left behind is needed.